Combination spare and service tail shaft assembly



N. LYRlTZlS Feb. 17, 1959 COMBINATION SPARE AND SERVICE TAIL SHAFTASSEMBLY Filed Dec. 27, 1957 INVENTOR. MAW/10f [He/72m AIME/VH4! nitedStates V COMBINATION SPARE AND SERVICE TAIL SHAFT ASSEMBLY t NikolaosLyritzis, New York, N. Y.

Application December 27, 1957, Serial No. 785,556 7 Claims. (Cl. 64-1)intermediate shaft. The power source of the ship is connected to theintermediate shaft which transmits rotary power to the propeller. It hasbeen found that after varying periods of service tirne'the conicalportion of the, tall or propeller shaft exterior of the stern tube orframe of the ship, and to which the propeller is keyed, will begin toshear or fracture. This fracture generally occurs at the forward end ofthe conical section of the tail shaft adjacent the propeller, which is ahigh stress area and subject to corrosion.

When a fracture of this type occurs while the ship is in a foreign portthe ship must remain in that'port until a replacement tail shaft can befabricated and sent to theship for installation. This disrupts the shipsschedule which is costly, often necessitating that the ship remain outof service for weeks. In order to decrease the period of time that aship is out of service when a fracture develops in the tail shaft, ithas heretofore been the practice for ships to carry a spare tail shaft.This enables a ship which has been disabled while distant from its homeport due to a fracturein the tail shaft, to proceed to the nearestdrydock and replace the fractured tail shaft with the spare. This hasthe advantage of enabling the ship to be put quickly back in service.The disadvantage, however, is thatthis practice necessitates thateachship carry a spare tail shaft which is expensive. These tail. shafts rcostapproximately $35,000 fora 70,000 tonship and represents aconsiderable standby investment.

In view of the foregoing it is the primary object of this invention toprovide a combination spare and service tail shaft assembly in which theconical end portion can be cut off; after a fracture occurs, a newconical end machined and the tail, shaft extended so that its length isequivalent to the lengthof the originaltailshaft assembly.

Another object ofthe present invention is to provide an insert for tailshaftassemblies which is inexpensive to fabricate as compared to thetail shaft, and which may be carried by ships in lieu of a spare tailshaft.

For a better understanding of the present invention as well as furtherobjects and features thereof, reference is made tothe fcllowing detaileddescription to be read in conjunction with the accompanying drawingswherein like components in the several views are identified by likereference numerals,

, Figure 1 is'a s de elevation of a tail shaft assembly presatent 7ently used, portions of the assembly being shown in cross section inorder to illustrate structural details.

Figure 2 is. a side elevation of the tail shaft assembly inaccordancewith the present invention. i

Figure 3 is a side .elevationof the tail shaft illustrated in Figure 2after a fracture has occurred in the conical end section. n

Figure 4 is a side elevation of the tail shaft illustrated in Figure 3after a new conical end section has been machined and the tail shaftmoved rearward such that the new conical section lies in the samevertical plane as the old conical section which has been removed.

FigureSis a side elevation of a tail shaft assembly embodying theprinciples. of the present invention, an insert having been providedbetween the tail and intermediate shafts, and n i t Figure 6 is ,aperspective view of the insert.

Referring now to the figures, and particularly to Figure 1, there isillustrated a tail of propeller shaft it and an intermediate ,Shaftill,as installed and used in present day steamships. The intermediate shaft11 is connected at its forward end tothe ships source of power (notshown) and is rotatively" supported in bearing 12.

The tail or propeller shaft which is designated generally by the numeral10, is coupled to the intermediate shaft 11 by bolts 13, andforms anaxial extension thereof. A bronze sleeve 14 annularly surrounds the tailshaft 10 andiprotects the tail shaft from corrosion. The tail shaft 10is. rotatively supported by the stern tube 15 which has a lining 16 witha low coefficient of friction, such for example aslignum vitae.'This'lining is held in position by a bronze sleeve .17. The, bulkheadof the ship .is designated generallyJat 18 and the annular gland at 19;the purpose ofthe latter beingtoprevent water from enters ing the ship.n

The rear end of the tail shaft 10 is formed with a conical sectionltl'towhich the propeller 21 is secured and.

held in positionby the bolt 22. A cap 23 protects the bolt 22 fromcorrosion. The foregoing are details of propeller shaft assemblies whichare well known to those skilled in the art.

After varyingperiods, ofservice time the tail shaft 10 will frequentlycrack or develop fractures in the conical end section 20 due tocorrosion and. concentration of stresses. These cracks or fracturesgenerally develop in the area of theconicalendsectionlti representingthe clearance between the fo-rwar d face of the propeller fzl and thestern tube 15, as illustrated in Figure 3. When a crack or fracture ofthis type occurs it has heretofore been the practice to remove the tailshaft 10 and replace it with a new one. In order to avoid excessivedelays virtually every ship today carries a spare tail shaft, whichrepresents a considerable'stand-by investment;

Previous efforts to repair and utilize a tail shaft after a crack orfracture develops in the conical end section have proven' impracticaland been thought impossible. This is due to therelative spacing betweenthebulkhead i8 and the flange 24 on the forward end of the tail shaftit? which hasheretofore prevented the tail shaft from being moved.rearward." This spacing is generally small since tail shafts are made asshort as-possible due totheir cost as compared to intermediate shafts.This is due to their greaterdiameteriand the cost of theliners.

The present inventionenables a tail shaftto continue in. service after acrack or fracture occurs: in the conical end section. This isaccomplished by initially installing a tail shaft 10 which. is longerthantail shafts. presently used. The length of. theintermediate shaft11' is decreased proportionately such thattthe overall length of thetailcand inte mediateshaft combination in accordance With the presentinvention is identical to that of existing assess"? tail andintermediate shaft combinations. In this manner the improved tail andintermediate shaft combination of the present invention may be installedon new or existing ships without necessitating any structural changes inthe bearings or mountings.

An extensible tail shaft in accordance with the present invention isillustrated in Figures 2.through 5. As illustrated in' these'figures,and particularly in Figure 2, the tail shaft of the present invention ismade longer than present day tail shafts, and greater in length thanthat required upon installation. The extension in length is designatedby the numeral 25 and is equivalent to, or slightly greater than, thelength of the conical end sec tion 20 and its threaded portion forengagement of the bolt 22, this length being designated generally by thenumeral 26. The intermediate shaft 11' of the present invention is madeshorter by the amount of the extension 25. In this manner the combinedlength of the tail and intermediate shaft of the present invention isequivalent to the combined length of presently used tail andintermediate shafts. This is illustrated from a comparison of Figures 1and 2;. The tail and inter-,

mediate shafts of the present invention may be installed in the samemanner as present shafts.

When the tail shaft of the present invention fracturcs or shears at theconical end section 20, such for example as at 27 illustrated in Figure3, the tail shaft 10' is uncoupled from the intermediate shaft 11' andremoved from the ship. The damaged conical end section is cut off atshoulder 28 and a new conical end 20' machined. As illustrated in Figure4 the tail shaft 10, after the removal of the conical end section 20' isthe same length as the presently used tail shafts 10.

After the new conical end 20' has been machined the tail shaft 10 isreinserted in the ship. Due to the removal of the conical end section20', however, the tail shaft 10' does not occupy its original positionbut is displaced rearward such that the propeller 21, when secured tothe conical end 20', will be in the same vertical plane as originally.When the tail shaft 10 is positioned in this manner the flange 24 of thetail shaft will be spaced from'the flange 29 of the intermediate shaftby the axial distance represented by the removal of the conical section20. This is best illustrated by Figure 4.

In order to couple the tail shaft 10' and the intermediate shaft 11together an insert shaft, generally designated by the numeral 30, isinterposed between the two. As illustrated in Figure 5 the axial lengthof this insert 30 is equal to, or slightly greater than the length ofthe conical end section 20 that was removed. This in sert 30, whenplaced in position, forms an axial extension of the tail andintermediate shafts and effectively couples these shafts together.

As can be seen from the foregoing, through the utilization of thepresent invention it is no longer necessary for a ship to carry anexpensive spare tail shaft. In lieu of a spare tail shaft all that theship must carry as a spare is the insert 30. This insert 30 requires nolining and cost approximately $2,000 as contrasted to $35,000 for a tailshaft fora 70,000 ton ship.

I claim:

1. A repairable shaft assembly comprising a tail shaft having a tailportion at one end thereof for mounting a propeller and a couplingportion at the other end thereof, an intermediate shaft engageablc, withsaid coupling portion to transmit rotary motion to said propeller, andan insert having an axial length corresponding substantiallyto that ofsaid tail portion and adapted to intercouple said coupling portion withsaid intermediate shaft to restore the length of said assembly to itsinitial value in the event it is necessary to sever the existing tail 7portion and to reform said tail portion on said tail shaft.

2 A repairable shaft assembly comprising a tail shaft having a tailportion at one end thereof for mounting a tail shaft having a conicaltail portion of predetermined,

propeller and a coupling flange at the other end thereof, anintermediate shaft engageable with the coupling flange of said tailshaft to form an axial extension thereof and transmit rotary motion tosaid propeller, and an insert shaft having an axial length correspondingsubstantially to that of said tail portion and adapted to intercouplcsaid coupling flange with said intermediate shaft to restore the lengthof said assembly to its initial'value in the event it is necessary tosever the existing tail portion and to reform said tail portion on saidtail shaft.

3. A repairable shaft assembly for transmitting rotary motion from apower source to a propeller comprising a tail shaft having a tailportion at one end thereof for mounting a propeller and a first couplingflange at the other end thereof, an intermediate shaft having a secondcoupling flange at one end thereof engageable with the first couplingflange of said tail shaft to form an axial extension thereof, the otherend of said intermediate shaft being linked to a power source totransmit rotary motion to said propeller, and an insert shaft having anaxial length corresponding substantially to that of said tail portion ofthe tail shaft, said insert having coupling flanges at each end, one ofsaid coupling flanges of 'said insert adapted to intercouple with thefirst coupling flange of said tail shaft and the other coupling flangeof said insert adapted to intercouple with the second coupling flange ofsaid intermediate shaft to restore the length of said assembly to itsinitial value in the event it is necessary to sever the existing tailportion and to reform said tail portion on said tail shaft. 7

4. A repairable shaft assembly for transmitting rotary motion from apower source to a propeller comprising a length at one end thereof formounting a propeller and a first coupling flange at the other endthereof, an intermediate shaft having a second coupling flange at oneend thereof engageable with the first couplingflange of said tail shaftto form an axial extension thereof, the other end of said intermediateshaft being linked to a power source to transmit rotary motion to saidpropeller, and an insert shaft having an axial length correspondingsubstantially to that of said tail portion of the tail shaft, saidinsert having coupling flanges at each end, one of said coupling flangesof said insert adapted to interc'ouple with the first coupling flange ofsaid tail shaft and the other coupling flange of said insert adapted tointercouple with the second coupling flange of .said intermediate shaftto restore the length of said assembly to its initial value in the eventit is necessary to sever the existing tail portion and to reform saidtail portion on said tail shaft.

5. A repairable shaft assembly for transmitting rotary motion from apower source to a propeller, said assembly comprising a tail shaft forsupporting said propeller and including a tail. portion at one end onwhich said pro-' peller is mountable anda coupling portion at the otherend thereof, an intermediate shaft engageable with the coupling portionof the tail shaft to link said propeller to a power source, said tailshaft having an axial dimension exceeding'the axial dimension of a givenstandard tail shaft by a predetermined length, and an insert having anaxial length corresponding to said predetermined dimension whichsaidtail shaft is lengthened to intercouple said tail shaft with saidintermediate shaft in the event said tail portion is severed from saidtail shaft and a new tail portion formed thereon whereby the lengthofjthe resultant assembly including said insert is, substantially thesame as the length of the original assembly before re moval of said tailportion. H g:

6. A repairable shaft assembly for transmitting rotary motion from apower source to a propeller, said assembly comprising a tail shaft forsupporting said propeller and including a tail portion at one end o'nwhich said-pro 'peller is mountable and a coupling" flange 'at theotherend thereof, an intermediate shaft engageable with the 5 coupling flangeof the tail shaft to form an axial extension thereof linking saidpropeller to a power source, said tail shaft having an axial dimensionexceeding the axial dimension of a given standard tail shaft by apredetermined length and said intermediate shaft having an axialdimension less than the axial dimension of a given standard intermediateshaft by said predetermined length, and an insert having an axial lengthcorresponding to said predetermined dimension by which said tail shaftis lengthened and said intermediate shaft is shortened to intercouplesaid tail shaft with said intermediate shaft in the event said tailportion is severed from said tail shaft and a new tail portion formedthereon whereby the length of the resultant assembly including saidinsert is substantially the same as the length of the original assemblybefore removal of said tail portion.

7. A repairable shaft assembly for transmitting rotary motion from apower source to a propeller, said assembly comprising a tail shaft forsupporting said propeller and including a conical tail portion at oneend of predetermined length on which said propeller is mountable and acoupling flange at the other end thereof an intermediate shaftengageable with the coupling flange of the tail shaft to form an axialextension thereof linking said propeller to a power source, said tailshaft having an axial dimension exceeding the axial dimension of a givenstandard tail shaft by the axial length of said conical portion and saidintermediate shaft having an axial dimension less than the axialdimension of a. given standard intermediate shaft by the axial length ofsaid conical tail portion, and an insert having an axial lengthcorresponding to the axial length of said conical tail portion tointercouple said tail shaft with said intermediate shaft in the eventsaid tail portion is severed from said tail shaft and a new tail portionformed thereon whereby the length of the resultant assembly includingsaid insert is substantially the same as the length of the originalassembly before removal of said tail portion.

References Cited in the file of this patent UNITED STATES PATENTS699,356 Verity May 6, 1902 1,139,182 Henthorn et a1 May 11, 19151,379,558 Hatfner May 24, 1921

